larger chainring for down hill

[paul b]

I was just wondering how many people are using a larger chainring for higher downhill speeds.the idea i have is use my motor to power up the big hills and use less battery by using a 52 tooth chainring and pedalling downhill I current use one on my racing bike for speeds up to 40 mph downhill so will hopefully fit one to my mtb conversion

 

[paul b]

Check out this item I found on eBay: http://pages.ebay.com/link/?nav=item.view&id=151283013643 this would do the job nicely

 

[flecc]

I like large chainwheels and to me a 52 tooth is perfectly normal for road use on any bike, including MTBs. On my last 700c wheel bike it gave me a top gear of 122 inches, allowing me to pedal up to 45 mph.

On my 20" wheel folder I have a 60 tooth chainwheel giving me a 92 inch top gear and allowing me to pedal to over 30 mph. Many small wheel bikes suffer from such low gearing that they are nearly impossible to pedal at over 15 mph.

So I'd say go for it, you still have the options of the two smaller chainrings for tougher going.

 

[RobF]

I don't fully understand gear inches, but have some experience of gearing from changing the sprocket and chain ring on the Rose.

My observation is a couple of teeth - particularly on the front - doesn't make much difference.

It depends what the OP is running at the moment.

But changing, say, a 50t to a 52t is hardly worth the bother.

 

[Artstu]

A lot of MTB's these days have around a 44 tooth large front sprocket, so a 52 will be worth it, having said that I fail to see how it is going to save any battery consumption?

I've just ordered a 16T rear sprocket, I've gone from 21T to 19T, which is OK, but feel a bigger gear could be even better, especially with tri-bars on

 

[paul b]

A lot of MTB's these days have around a 44 tooth large front sprocket, so a 52 will be worth it, having said that I fail to see how it is going to save any battery consumption?

I've just ordered a 16T rear sprocket, I've gone from 21T to 19T, which is OK, but feel a bigger gear could be even better, especially with tri-bars on

Defo worth it I just thought you could assist the motor at an higher speed with the larger chainring and use it with the motor running to help batt consumption I am probably wrong as ive never ridden an ebike/conversion so all this is new to me

 

[flecc]

If the larger chainring enables you to pedal faster downhill, and in consequence the kinetic energy carries you further along the following flat of up the following hill, you will save a bit of battery content and slightly extend your range.

By contrast, an undergeared e-bike can be very thirsty if it means the rider is unable to adequately help through pedalling at all speeds. For example, one undergeared small wheel folder manages only 15 miles range on it's 370 Wh battery due to the rider's pedalling being unable to keep up with the motor's speed.

That leaves the motor doing nearly all the work so a consumption of 25 Wh per mile, double the usual average for most e-bikes.

 

[paul b]

I like large chainwheels and to me a 52 tooth is perfectly normal for road use on any bike, including MTBs. On my last 700c wheel bike it gave me a top gear of 122 inches, allowing me to pedal up to 45 mph.

On my 20" wheel folder I have a 60 tooth chainwheel giving me a 92 inch top gear and allowing me to pedal to over 30 mph. Many small wheel bikes suffer from such low gearing that they are nearly impossible to pedal at over 15 mph.

So I'd say go for it, you still have the options of the two smaller chainrings for tougher going.

That 60 tooth looks a beast it would be nice to get a triple cog with that on

 

[flecc]

That 60 tooth looks a beast it would be nice to get a triple cog with that on

Could do, since it's on a standard OCD 5 spoke spider. The chainring was by Zenith of France.

I didn't need a triple on that particular bike since it's beast of a hill climber already. Up to 12% gradient I don't even need to pedal, and it will even restart on 12% using motor only.

 

[paul b]

Could do, since it's on a standard OCD 5 spoke spider. The chainring was by Zenith of France.

I didn't need a triple on that particular bike since it's beast of a hill climber already. Up to 12% gradient I don't even need to pedal, and it will even restart on 12% using motor only.

Youve got me thinking now lol

 

[flecc]

Youve got me thinking now lol

That chainring cost over £90.

That's stopped you thinking!

 

[paul b]

Yes lol i will stick with my 52 option my 44 tooth as got to go and think time trial bars would be a good option to keep low

 

[rippedupno1]

@ Artstu
A lot of MTB's these days have around a 44 tooth large front sprocket, so a 52 will be worth it, having said that I fail to see how it is going to save any battery consumption?<br /><br />I've just ordered a 16T rear sprocket, I've gone from 21T to 19T, which is OK, but feel a bigger gear could be even better, especially with tri-bars on <br/>
Is this so you can blasting past me on the flat on the tt course we're going to do? Lol

 

[Artstu]

Is this so you can blasting past me on the flat on the tt course we're going to do? Lol

Could be I want to try and beat the course record, I'm just 3 minutes off.